1. Field of the Invention
The present invention relates to an iron golf club set.
2. Description of the Related Art
In general, an iron golf club set is composed of a plurality of iron golf clubs having respective club numbers different from each other. The iron golf club set is composed for example of 10 clubs, i.e., seven iron clubs of No. 3 to No. 9 and three wedge clubs of a pitching wedge, an approach wedge and a sand wedge.
The sole width of each of these iron golf clubs has a great influence on a position of center of gravity of the iron golf club.
Description will be given below of sole widths of the numbered clubs of the conventional iron golf club set with reference to FIG. 14. FIG. 14 is a graph illustrating a relationship between the numbered clubs of the conventional iron golf club set with their sole widths. An abscissa of the graph represents a number of the club and an ordinate represents a sole width. In FIG. 14, "X" indicates a straight solid line connecting values of sole width of the respective numbered clubs of the conventional iron golf club set (hereinafter referred to as the "prior art 1"), "Y" indicates a straight dotted line connecting values of sole width of the respective numbered clubs of another conventional iron golf club set (hereinafter referred to as the "prior art 2"), and "Z" indicates straight one-point chain lines connecting values of sole width of the respective numbered clubs of further another conventional iron golf club set (hereinafter referred to as the "prior art 3").
As is clear from FIG. 14, in the prior art 1, the sole widths of the iron golf clubs gradually increase from No. 3 iron club toward a sand wedge. On the contrary, in the prior art 2, the sole widths of the iron golf clubs gradually decrease from No. 3 iron club toward the sand wedge. In the prior art 3, the sole widths of the iron golf clubs gradually decrease from No. 3 iron club toward No. 5 iron club, while the sole widths thereof gradually increase from No. 5 iron club toward the sand wedge.
However, in the prior art 1, it is hard for a golf player to hit a golf ball with the use of the lower lofted irons, especially the so-called long iron clubs of No. 3 to No. 5 irons, thus requiring a skilful technique for using such lower lofted irons efficiently. Such a tendency will be described with reference to FIG. 15. The lower lofted iron club of the iron golf club set of the prior art 1 has a narrow sole width W2. Accordingly, the center of gravity G2 of the head H has a tendency to be apart upward from the sole 8 by the long distance H2 and to come close to the face 7, resulting in a smaller value of depth of the center of gravity, i.e., the shorter horizontal distance D2 from the leading edge 11 to the center of gravity G2. The sweet spot of the iron golf club therefore becomes narrower, leading to difficulty to hit, and making it hard to increase the trajectory of the resultant ball flight after being hit by the club. In FIG. 15, "S" is a shaft, "9" is a hosel and "10" is a back face.
On the contrary to the prior art 1, in the prior art 2, it is hard for a golf player to hit a golf ball with the use of the higher lofted irons, especially the so-called short iron clubs of from No. 9 iron to the sand wedge, thus requiring a skilful technique for using such higher lofted irons efficiently.
In the prior art 3, although the lower lofted iron club has a relatively long sole width, thus improving in hitting properties, the sole width of the lower lofted iron club is, at the most, substantially identical with the sole width of the sand wedge, thus making it still hard for an average recreational golf player to use such a club efficiently.